1. Field of the Invention
The present invention generally relates to information reproducing apparatuses, data management information obtaining methods, data management information obtaining programs, and storage media that reproduce data requested by users from recordable information recording media such as DVD+Rs.
2. Description of the Related Art
Recently, with the improvement of their functions, personal computers (PCs) have been able to handle AV (Audio-Visual) information such as music and images. Since the amount of the AV information is very huge, optical discs such as CD-R (Compact Disc-Recordable) and DVD+R (Digital Versatile Disc+Recordable) have been attracting attention as information recording media. As the prices of the optical discs have been reduced, optical disc devices as information reproducing apparatuses have become widely used as one of the peripheral devices of the PCs.
There is the Universal Disc Format (UDF) standard as a file system using recordable information recording media such as CD-Rs and DVD+Rs. The UDF is the file system used for various devices and utilizing a record format that takes advantage of a characteristic of each device. Especially, CD-Rs and DVD+Rs apply the sequential UDF in which data are sequentially recorded from the inner side of a disc, since CD-Rs and DVD+Rs are write-once types that do not allow overwriting of data.
Generally, in the sequential UDF, in order to maintain the compatibility with ISO 9660, the first track is reserved and data requested from a user are incrementally written from the second track. That is, the multi-track recording system that records data by dividing a session into a plurality of tracks, which form recording units, is used.
In the above-described recording state in the sequential UDF, since an unrecorded area exists in a session, reproduction is possible only by an information recording/reproducing apparatus, and it is impossible to reproduce using an information reproducing apparatus such as a CD-ROM drive or a DVD-ROM drive. However, when file system information of record data is recorded to the first track (record file information for achieving compatibility with ISO 9660), and lead-in/lead-out is recorded and closed, it is possible to reproduce the data by a CD-ROM drive and a DVD-ROM drive. Further, CD-Rs, DVD+Rs and the like use the multi-session recording system so as to further write to such discs in which sessions are closed.
In the CD-R, the maximum track number is limited to 99 tracks, which is a small number. Thus, irrespective of the number of sessions, information of the tracks existing all over the disc is recorded in an area called program memory area (PMA). Accordingly, it is possible to manage the information of all the tracks. Hence, in a CD-R, it is possible to immediately report the information of a track requested by the user by storing, in the memory of a drive unit, the track information obtained from the PMA.
On the other hand, the DVD+R allows recording of up to 191 sessions in the record area. Each of the sessions allows recording of up to 16 tracks (referred to “fragments” in the DVD+R). That is, up to 3056 (=191×16) fragments, which is a vast number, can exist on a DVD+R. Additionally, in the DVD+R, a lead-in of the second session (and later sessions) is called an “intro”, and a lead-out before the last session is called a “closure”. Information (fragment number, start address of fragment, last address of fragment and the like, which are hereinafter referred to as “fragment information”) relating to fragments in each session is recorded in a management information area called session disc control block (SDCB) that is recorded in the lead-in (or the intro) of the session. The SDCB includes information (session number, start address of session, last address of session and the like) relating to all sessions before the session as well as all fragment information of the session.
That is, in the DVD disc such as a DVD+R and DVD+RW, disc control blocks (DCBs) indicating the record state of the disc exist, and a means for reporting DCB information to the user is prepared. In the DVD+R, as mentioned above, there are the DCBs such as the SDCBs that include information of all sessions existing on the disc and information of all fragments existing in the session. In addition, in the DVD+RW, there is a formatting disc control block (FDCB) having information of the format state and the like. Since it is possible to overwrite the DVD+RW, when the format state is changed, the FDCB is overwritten and updated. On the other hand, since the DVD+R is a write-once disc that cannot be overwritten, the SDCB is updated and recorded in a predetermined new SDCB area every time a session or a fragment is added.
By the way, there is a case where an upper device (for example, a PC) using such an optical disc device requires, prior to reproducing an optical disc, management information relating to data recorded on the optical disc. Thus, the upper device is configured to be able to request, from the optical disc device, the management information (number of sessions included in the record area and the like, which are hereinafter referred to as “session information”) relating to sessions of the optical disc and information (number of tracks included in the record area, track address indicating a track position, and the like, which are hereinafter referred to as “track information”) relating to tracks.
Corresponding to this, when the optical disc is a DVD+R, for example, the optical disc device reports the above-described fragment information to the upper device in response to a request for the track information from the upper device. Also, when the optical disc is a CD-R, the optical disc device obtains the answer for a request for the track information from the upper device based on the track information recorded in the PMA as described above.
However, when the optical disc is a DVD+R, for example, as mentioned above, the fragment information is recorded in the SDCBs corresponding to the respective sessions. Thus, it is necessary for a conventional optical disc device to sequentially search the SDCBs in the respective sessions dispersed in the record area. Accordingly, there is a problem in that the speed of response with respect to a track information obtaining request from the upper device, that is, the performance is significantly degraded.
Therefore, it is conceivable to obtain all fragment information in advance when an optical disc is set to the drive unit. However, because of a similar reason as in the case above, a considerable amount of time is required for obtaining all fragment information. Thus, there is a problem in that time until user access is made possible after the optical disc is set to the drive unit, so called disc mount time, is increased. Further, as mentioned above, the DVD+R allows up to 3056 fragments to exist thereon. For this reason, considering the memory capacity, it is difficult to store all fragment information in the memory of the drive unit.
Additionally, even in a case where designated fragment information is read from the disc when the user makes a request for the fragment information, since the fragment information exists in the SCDBs of the respective sessions in a dispersed manner as mentioned above, it is necessary to sequentially search for the SCDBs having the designated fragment. In this case, the performance with respect to the request for the fragment information by the user is significantly degraded.
Regarding such problems, for the DVD+R, a method has been proposed and is to be adopted as the standard where a session of which data recording is completed (closed session) is reported as one track to the user even when a plurality of fragments exist in the session. That is, when an obtaining request for the management information includes a request for obtaining the number of tracks, each of the closed sessions among the sessions included in the record area is regarded as one track (a pseudo-track) so as to calculate the number of tracks in response to the request. This is because there is no concept of the track in the DVD, the fragment in the DVD+R is for data recording, and thus individual fragment information in the session of which data recording is completed is not important. In other words, when recording data, a write-once type disc such as the DVD+R requires information (fragment information) of tracks existing in sessions (open sessions) of which data recording is not completed. However, information (fragment information) of tracks in closed sessions to which data recording cannot be further performed is not important. Thus, there is no inconvenience if the number of the closed sessions is given as an answer to the track number obtaining request.
As a result, it is not necessary to check SDCBs in all sessions with respect to the management information obtaining request. It is possible to immediately obtain the number of the pseudo-tracks only from the SCDB in the last session. Consequently, the number of tracks is, at the maximum, 206 (=190 (the number of the pseudo-tracks)+16 (the number of tracks in an open session)). Thus, as in the case of the CD-R, it is possible to store information of each track in the memory of the drive unit in advance. Accordingly, a method is used in which, with respect to the management information obtaining request by the user, management information recorded in the SCDB of the last session is always reported.
However, despite such a DVD+R environment, there may still be a request for obtaining individual fragment information in the closed sessions. For example, depending on a category where the drive unit is used, a case exists where there is a request for obtaining individual fragment information in the closed sessions so as to confirm the fragment information in data recording and the like.
In such a case, with respect to the management information obtaining request by the user, though the session information of the prior sessions is obtained, it is impossible to obtain the fragment information of the prior sessions, even if the management information is obtained from the SDCB of the last session. In other words, there is a problem in that the user cannot obtain individual fragment information in the closed sessions, since a means for reporting to the user the contents of the SDCBs of desired sessions does not exist, though individual fragment information in the closed sessions exists only in the SDCBs of the corresponding sessions.